A screen of the type defined above is already known and is formed by a fabric of non-woven material of which one face is provided with a print by ink jets, marking the fibers without forming a film between the fibers.
Such a screen is distinguished from screens formed by canvas sheets, that is to say textile surfaces generally consisting of a polyester fabric provided with an impervious coating of polyvinyl chloride (PVC) so that it has a surface which is impermeable to air.
In fact, according to certain regulations currently in force, surfaces such as canvas sheets or screens which are installed externally, in front of buildings or in isolation, must permit a certain passage of wind in order to reduce the forces exerted by the wind on these surfaces and the structures which support them.
For this, the canvas sheets must have passages, generally in the form of U-shaped cut-outs, which form flaps which are free to open in order to make the openings available for the passage of air. According to certain regulations, the surface thus freed in the total surface of the canvas sheet is less than 10% of the total surface of the canvas sheet.
There are already in existence screens with a decorative surface which are formed by a non-woven fabric on which the decoration has been printed by monochrome or polychrome printing by ink jets.
However, although these known screens which are formed from a non-woven fabric are of more interest than canvas sheets because they necessitate less resistant support structures for stability in the wind, they do nevertheless have a certain number of drawbacks. First of all, since the material itself is relatively porous it functions as a filter and dirt accumulates in the thickness of the non-woven fabric.
For example, it is known (according to EP 0 704 315) to produce a printing substrate made from a fibrous product coated with porous particles having dimensions varying from 0.1 to 30 μm, and a surface layer made from boehmite. However, such a layer to receive the ink is not air-permeable or at least it is not sufficiently so in order to form an external screen.
Furthermore, ink jet printing, which penetrates more or less and spreads through a relatively substantial thickness of the non-woven fabric, does not give an image which is as precise and clear as one might wish since certain of the printing droplets penetrate too deeply into the non-woven fabric to be perceptible on the exterior. This can spoil the sharpness of an outline or the colour which is produced by ink jets and results from the combination of primary shades.
Finally, since the ink jets are projected according to a certain firing line, if the image is not viewed from the same angle the image seen will not have the desired sharpness due to this “in depth” printing.
Finally, when these screens have substantial surface areas they lack resistance and can deform or collapse.